Ultraviolet radiation can be effectively used as a means for a final disinfection of water being dispensed from a water source.
In order to be fully effective, the ultraviolet radiation source must act upon the water up to and including the point at which the water actually exits the spout. A portion of water residing just inside the spout can be exposed to contamination if this does not happen.
The amount of time for the UV source to reach an effective power level after being energized will vary, depending upon the specifics of the UV source used. A consequence of this is that many water dispensing units will keep the UV source energized. While this maintains the disinfection level of the water, it also raises the temperature of the water in the disinfection zone. This is an undesired effect, particularly when the first portion of water being dispensed from a water cooler is actually warmer than ambient. One way to minimize this effect is to limit the volume of water in the disinfection zone when no flow is occurring. However, there are also normal flow rates expected by consumers when using the dispenser. If the volume of water subject to disinfection at any point is being minimized, then the residence time in the disinfection zone is also very low, reducing the effect of the UV radiation.
It is therefore an unmet advantage of the prior art to provide a spout for a water dispensing unit that extends the UV radiation as close to the tip of the spout as possible, minimizes the amount of water dispensed at a temperature above ambient, and provides the needed residence time to disinfect, while maintaining an acceptably high flow rate.